Hi all, I'm studying simple Audio Player in order to output a wave table.after I strip the unnecessary stuff, the sketch works once. not repeatedly.can anybody spot the problem ?

when looking at the audio.cpp and daq.cpp, I noticed isrId. it seems it is never given it's proper value (38 I believe ?).But I'm a newbie on cpp, can anybody check and tell me where this variable is set, or why the programming is OK without giving it a value ?